Production and characterization of monoclonal antibodies against carcinoembryonic antigen (CEA)

In the experiments presented here 22 monoclonal antibodies (MoAbs) were produced which reacted with the tumor marker carcinoembryonic antigen (CEA). Eleven of the MoAbs reacted neither with peripheral blood granulocytes nor with purified spleen NCA-60 kDa and were therefore regarded as "CEA-specific". Only three antibodies of this group reacted exclusively with CEA-180 kDa. Eight MoAbs reacted with CEA-180 kDa and with CEA-like substances of lower molecular mass (of 160 kDa and/or 120 kDa) present in colon carcinoma cells as determined by immunoblotting. These molecules seem to be different from the classical non-specific cross-reacting antigens (NCAs) present in peripheral blood granulocytes. In contrast to that, the other 11 anti-CEA MoAbs recognized in addition to CEA-180 kDa also NCAs on granulocytes. Six of them were reactive with a purified spleen NCA-60 kDa preparation. These MoAbs bound also to reduced and alkylated CEA-180 kDa (CEA r/a), i.e. they recognize sequential epitopes. All 22 MoAbs reacted with CEA expressed in different human tumor cell lines as determined by immunocytological analysis. But six of them did not bind to the surface of these cells when tested in a radioimmuno-binding assay. It was concluded that the epitope(s) recognized by these antibodies are involved in cell membrane anchoring of the CEA-molecules.